Many integrated circuits (ICs) in a given electronic device have different functions and can operate at different frequencies. Typically, all ICs and/or all parts of a given IC may receive a voltage potential that is substantially uniform. However, the market for consumer electronics is constantly improving. There is an increasing demand for smaller circuit packages that operate at increased speeds and consume less power for the purpose of conserving battery-life, such as in wireless communication applications. As such, one manner of conserving power is adaptive voltage scaling (AVS), such that different ICs, or even different portions of a single IC, can operate with a voltage that is optimized for application use. Accordingly, power is conserved in the electronic device by not applying more than sufficient power for a given one or more of the ICs, according to the application use.
Through switching of semiconductor devices, the semiconductor material from which the semiconductor devices are made ages. As the semiconductor material of the IC ages, the transistors formed therein can be subject to deleterious effects. For example, PMOS transistors can be subject to negative biased temperature instability (NBTI), such that larger DC gate-to-source voltages are required for activation of the PMOS transistors. As another example, NMOS transistors can be subject to channel hot carrier (CHC) effects, such that the NMOS transistors can be affected with higher slew, resulting in slower switching transitions at constant bias voltages. Because of the effects of semiconductor aging, higher voltage levels may be required for the transistors of the IC to operate with the same performance as during production testing. In applications where a uniform voltage is provided to all ICs or all portions of an IC, the applied voltage can be chosen to be more than sufficient for the applications by being selected for a worst case scenario at the expense of power consumption.
In addition, environmental changes and process variations may change operating characteristics for a given IC, even subsequent to production testing of the given IC. For example, differences in transistor strength and performance variations may dictate different characteristic values that affect frequency of operation from one IC to another. In addition, the process variations from one semiconductor wafer to the next may be such that operating characteristics can be significantly different for the dies on the respective wafers, and thus the resulting ICs on the respective wafers. Different characteristic values can be adjusted through operating software of a given IC. However, as the environmental changes and process variations can be very frequent and/or ubiquitous, making adjustments to characteristic values via software can be time consuming, expensive, and/or impractical.